1. Field of the Invention
The present invention relates to a treatment solution used for a pretreatment for analyzing an object in a sample, a method for the pretreatment, a method for acquiring information on the object in the sample, and a method for detecting the presence of a specific object. Especially the present invention relates to a treatment solution used for a pretreatment for analyzing a protein contained in a tissue or a cell, a method for the pretreatment, a method for acquiring information on the protein contained in a tissue or a cell, and a method for detecting the presence of the protein.
2. Description of the Related Art
The recent progress in genome analysis has been rapidly highlighting the importance of analyses of proteins in the living body as gene products.
The importance of analyzing expression and function of a protein has been long recognized, and development of analysis methods therefor has been continued. Fundamentally, they are based on the combination of the techniques of:    (1) separation and purification by two-dimensional electrophoresis or high performance liquid chromatography (HPLC), and    (2) a detection system, such as a radioactivation analysis, an optical analysis, a mass spectrometry.
The basic protein analysis technology is called proteome analysis, which is aimed at analyzing a protein produced by a gene and functioning actually in vivo, and discovering a cell function or the cause of a disease. An example of a typical analysis technique includes:    (1) extraction of a protein from a tissue or cell of interest,    (2) separation of the protein by a two-dimensional electrophoresis,    (3) analysis of the protein or its fragments by a mass spectrometry, such as a matrix-assisted laser desorption ionization time-of-flight mass spectrometry (an MALDI-TOFMS), and    (4) identification of the protein using a database, as from a genome project.
An additional example includes:    (1) extraction of a protein from a tissue or cell of interest,    (2) digestion (or denaturation) of the extracted protein,    (3) analysis of the digested (or denatured) protein by a combined system of a liquid chromatography (LC) and an Ion-trap mass spectrometry (Ion-trap MS), and    (4) creation of a database and identification of the protein. (“Experimental Medicine, Separate Volume, Proteome Analysis”, edited by Toshiaki Isobe and Nobuhiro Takahashi, Yodosha Co., Ltd., 2000)
For example concerning cancer, such a positive result is being obtained, that a protein related to recurrence or metastasis is becoming uncovered owing to a proteome analysis.
The present inventors proposed a method and an apparatus for acquiring information based on a time of flight secondary ion mass spectrometry (hereinafter abbreviated as “TOF-SIMS”) aiming at visualization of a two-dimensional distribution of a protein on a protein chip or a tissue slice (Japanese Patent No. 3658397). By this method, an ionization promoting substance and/or a digestive enzyme is applied by an ink-jet technique to the protein chip or the tissue slice, and information on an identity of the protein (including information on peptides restrictively proteolyzed by the digestive enzyme) is to be visualized by TOF-SIMS maintaining the positional information.
The present inventors have proposed certain developments of the method and apparatus. Namely, an improvement concerning pH of an aqueous solution used by an ink-jet technique, an improvement concerning detection of an intracellular metabolite, and an improvement concerning identification ability for a protein by a combined use of separation and purification techniques, such as electrophoresis or thin-layer chromatography.
To improve the detection sensitivity of TOF-SIMS, a method of using metal particles has been proposed. For example, A. Marcus and N. Winograd reported that the detection sensitivity was improved by depositing nano-particles of gold or silver on the sample surface forming a sub-monolayer (A. Marcus and N. Winograd, Anal. Chem., 78, 141-148 (2006)). Further, Y. P. Kim et al. reported that the ionization efficiency (by TOF-SIMS) of a peptide molecule located on a nano-particle of gold was enhanced by the effect of the gold nano-particle (Y. P. Kim et al., Anal. Chem., 78, 1913-1920 (2006)).
Examples of an SIMS analysis aiming at a single cell include a report by S. G. Ostrowski et al. (S. G. Ostrowski et al., “Single-Cell Level Mass Spectrometric Imaging”, Dekker Encyclopedia of Nanoscience and Nanotechnology, pages 1-11 (2006)).
Further, Japanese Patent No. 3207706 discloses a method, by which an aqueous solution containing a metal colloid is applied in a form of droplets to a substrate by an ink-jet method.